ext3: use proper little-endian bitops

ext3: use proper little-endian bitops

ext3_{set,clear}_bit() is defined as __test_and_{set,clear}_bit_le()
for ext3.  But all ext3_{set,clear}_bit() calls ignore return values.
So these can be replaced with __{set,clear}_bit_le().

This changes ext3_{set,clear}_bit safely, because if someone uses
these macros without noticing the change, new ext3_{set,clear}_bit
don't have return value and causes compiler errors where the return
value is used.

This also removes unused ext3_find_first_zero_bit().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>